Jeholornis
was a primitive bird that is known from both the Hebei and Liaoning
provinces of China where individuals of the genus lived during the
early cretaceous.‭ ‬At eighty centimetres long from the tip of the
snout to the tip of the tail,‭ ‬Jeholornis was
quite a large bird for
the time.‭ ‬Two additional bird genera named Shenzhouraptor
and
Jixiangornis‭ (‬also both named in‭ ‬2002‭) ‬are now
regarded as
synonyms to Jeholornis.‭ ‬There has been previous
dispute over whether
Shenzhouraptor should have priority over Jeholornis
since they were
both named so closely together with Shenzhouraptor
appearing in a
monthly journal and Jeholornis in a weekly one,‭
‬but‭ ‬Jeholornis is
usually treated as valid since in these circumstances weekly journals
are seen to have technical priority.Jeholornis
was similar to genera such as Epidexipteryx
and Incisivosaurus‭
‬since
those individuals‭ ‬also‭ ‬had short but high skulls.‭ ‬The jaws curved
downwards and depending upon the fossil specimen,‭ ‬show a greatly
reduced amount of teeth.‭ ‬The holotype specimen only possessed three
pairs of reduced blunt teeth in the lower jaw,‭ ‬while another suggests
no teeth at all.‭ ‬These were likely feeding adaptations that allowed
Jeholornis to pluck up and swallow seeds,‭
‬something that can be
supported by the discovery of around fifty,‭ ‬eight to ten millimetre
seeds believed to be from the plant genus Carpolithes
inside what was
once the crop of a Jeholornis.Jeholornis
had better developed wings than earlier bird forms such as
Archaeopteryx,‭
‬though they were still not as well adapted for true
flapping flight as the wings of modern birds are.‭ ‬The wings were
still longer than the legs,‭ ‬and the feathers were asymmetrical
similar to modern birds.‭ ‬Like with many primitive forms,‭ ‬gliding
flight would have certainly been possible for Jeholornis,‭
‬but it is
still unknown if it could use flapping flight since the arrangement of
the shoulders would have still had a limited range of motion hindering
a flight stroke where the wings passed above the back.Jeholornis
still lacked a pygostyle and instead had a long more dinosaur-like
tail.‭ ‬This feature would not have made flight impossible,‭ ‬but it
would not have been as good as a pygostyle that supported the growth of
flight feathers from the tail.‭ ‬Analysis of the bones of Jeholornis
also indicate that individuals grew very slowly,‭ ‬another primitive
trait shared with other early bird forms,‭ ‬though as the Cretaceous
period went on birds would develop to become very fast growing animals.
One
of the key important things about Jeholornis is
that the hallux‭
(‬first toe‭) ‬is partially reversed meaning that it was semi
opposable.‭ ‬In modern birds the hallux is completely opposable to the
other toes so that a bird can grip hold of branches,‭ ‬in a similar
manner to how you can hold onto railings by wrapping your thumb and
fingers around them.‭ ‬Jeholornis would not have
been as capable of
this as modern birds,‭ ‬but again more primitive forms such as
Archaeopteryx lacked an opposable hallux all
together and could not
perch like modern birds at all.‭ ‬Therefore the hallux of Jeholornis
shows the continuing transition to the modern bird form,‭ ‬helping to
fill in another gap in the evolutionary theory of dinosaurs to birds.

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